minor update

Performance-Tuning.md

@@ -249,6 +249,7 @@ net.ipv4.tcp_slow_start_after_idle = 0
 # Allow reuse of sockets in TIME_WAIT state for new connections only when it is safe from the network stack’s perspective. Default: 0
 net.ipv4.tcp_tw_reuse = 1
 # Do not last the complete time_wait cycle. Default: 0
+# only works from Linux 2.4 to 4.11
 net.ipv4.tcp_tw_recycle = 1
 # Minimum time a socket will stay in TIME_WAIT state (unusable after being used once). Default: 60
 net.ipv4.tcp_fin_timeout = 30